Syrian President Bashar al-Assad said he and his government would survive the civil war having endured everything his opponents could do to topple him, and only the distant prospect of direct foreign military intervention could change that.

"This was their goal in hitting our infrastructure, hitting our economy, and creating complete chaos in society so that we would become a failed state," Assad said in an interview with Syria's official Thawra newspaper published on Thursday.

"So far we have not reached that stage."

The only factor that could undermine the resilience of the government, he said, was direct foreign intervention. But he said that was a unlikely due to foreign powers' conflicting views of an opposition movement increasingly overtaken by radical Islamist militants.

"They have used every material, emotional and psychological means available to them. The only option they have is direct foreign intervention," he said.

"But there is hesitation and rejection (of intervention) from most countries so if we can overcome this stage with resoluteness and awareness, we have nothing more to fear."

Syria's two-year uprising against Assad, whose family has ruled Syria for more than four decades, began as peaceful protests but became militarised after an army crackdown.

The rebels remain strong in the north of Syria, but Assad has been slowly reinforcing his forces there in the hope of retaking territory. Fierce fighting is raging around several cities in central Syria and near the capital.

Assad's counter-offensive led the United States to announce last month military support for the opposition, a move it said would restore the balance of power ahead of any peace talks.

The United States and Russia, Assad's main weapons supplier, have proposed a "Geneva 2" peace conference but their deadlock over Syria has meant little progress on the diplomatic front.

Despite what the president acknowledged was widespread suffering in his country, he said his government and its supporters had proved they could weather the storm.

Assad said the country's ability to avoid "failed state" status was due in large part to Syrian businessmen and workers who continued to do their jobs despite the chaos.

"The Syrian people remain unbroken in every sense of the word. There is an explosion, and within minutes of the clean up, life goes back to normal," Assad said. "They go to work even as they expect terrorist rockets and terrorist explosions and suicide bombings to happen at any moment."